---
description: How to setup and use the TriplitClient in the browser to sync data.
---

# Triplit Client

Triplit is most powerful when it is used to sync data across multiple devices and users. Every Triplit Client is equipped with a sync engine that is responsible for managing the connection to the server and syncing data between your local database and remote database.

## Installation

```bash
npm install @triplit/client
```

## Client and Server model

As the monicker, "a full-stack database" implies, Triplit has components that run on both the client and the server. In particular, each client has its own database that is fully queryable just like the remote database. Thus, any query can be immediately fulfilled by the client without needing to go to the network. The client database is kept in sync with the remote database by setting up subscriptions to queries.

Along with reads, every client is able to write to its database and Triplit ensures the write is propagated to the remote database and other listening clients. Because writes go directly to the client database, your application gets an optimistic effect to all of its writes.

### Client Database

On the client, Triplit keeps your data in two storage areas: an `outbox` and a `cache`. The outbox is a buffer of data that is waiting to be sent to the server. The cache is a local copy of the data that has been confirmed to have been received by the server.

By default, results from the cache and outbox are merged together, however queries can be configured to only return data from the cache (to display only confirmed data) or only return data from the outbox (to denote unconfirmed data).

If a client is offline or is not connected to the remote database for any reason, then the data will remain in the outbox so that data can be synced at a later time.

### Server Database

The server database provides durable centralized storage for clients and handles propagating writes to other listening clients. As well, the server acts as an authoritative figure for data as needed. For example, access control rules are checked on the server and unauthorized updates are rejected and not propagated.

## Setting up sync

To set up syncing, you need to tell your Triplit Client how to connect to the remote database with the `serverUrl` and `token` options in the constructor. Additional options can be found [here](/client/options).

```typescript
const client = new TriplitClient({
  serverUrl: '<remote database URL>',
  token: '<access token>',
});
```

## Example

[Once you've installed](/getting-started) the Triplit CLI, you can run the following command to start a local Triplit Server (and remote database):

```bash
npm run triplit dev
```

By default this will set up a server at `http://localhost:6543`, and should display an access token for your database.

You can run this script in multiple browser tabs to simulate multiple users/devices connecting and sending data.

```typescript
import { TriplitClient } from '@triplit/client';

const client = new TriplitClient({
  serverUrl: 'http://localhost:6543',
  token: '<access token>',
});

const query = client.query('todos');

client.subscribe(query, (todos) => {
  console.log(todos);
});

client.insert('todos', {
  text: 'My Todo',
  createdAt: new Date().toISOString(),
});
```
